1. Field of the Invention
The disclosures herein relate to a switching converter circuit configured to output a predetermined constant voltage by a switching operation.
2. Description of the Related Art
Initially, a related art switching converter circuit is described. FIG. 1 is a diagram illustrating the related art switching converter circuit.
As illustrated in FIG. 1, a switching circuit converter circuit 10 includes input terminals Vin1 and Vin2, switches SW1, SW2 and SW3, a backflow preventer circuit 1, and an inverter 2. The switch SW1 supplies electric charges to a coil via the input terminal Vin1 when the switch SW1 is in ON-cycle. The switch SW2 supplies electric charges to the coil via the input terminal Vin2 when the switching converter circuit 10 is OFF-cycle. The switch SW3 is cascade connected to the switch SW2.
ON/OFF of the switch SW1 is controlled by a control signal S1 supplied from a terminal T1, and ON/OFF of the switch SW2 is controlled by an inverted signal obtained by the inverter 2 inverting the control signal S1. ON/OFF of the switch SW3 is controlled by an output signal supplied from the backflow preventer circuit 1.
In the related art switching converter circuit 10, the backflow preventer circuit 1 corresponds to a comparator, and the switch SW3 is controlled by the output signal supplied from the comparator. Further, the backflow preventer circuit (comparator) 1 is configured to detect a voltage between the input terminals Vin 1 and Vin2, a voltage between both ends of the switch SW2, or a voltage between both ends of the switch SW3 so as to detect the backflow of the electric current based on the detected voltage. Japanese Patent Application Publication No. 2008-67495 discloses a switching regulator, an example of which is illustrated as the switching circuit converter circuit 10 in FIG. 1.
However, when the voltage of the backflow preventer circuit actually produced is measured, the measured voltage may be varied. As a result, the current actually operating the backflow preventer circuit may be varied.
For example, a preferable characteristic that may be required for the switching converter circuit utilized in devices such as mobile phones may be efficiency. In order to improve the efficiency of the switching converter circuit in a light loaded mode, the generation of the backflow current may need to be prevented when the switching converter circuit is OFF-cycle. However, it may be difficult to design the switching converter circuit having the above configuration to reduce the backflow current approximately to 0 in order to improve the accuracy of the backflow preventer circuit.